The present invention relates to pattern-wheel control of flat-bed knitting-machine operation, and in particular to the use of a pattern wheel on a cam carriage for the specific purpose of shifting selected needles in a direction away from the knitting cam system of the carriage.
In terms of implementation, the invention is at least presently concerned with a type of knitting machine in which the shanks of the needles in the needle bed extend through guide passages in pattern bolts. The pattern bolts extend in a direction which is transverse to both the direction of needle elongation and the direction in which the cam carriage travels. Jacks on the pattern wheel are selected, by a jacquard mechanism. The selected jacks engage the pattern bolts of certain needles, and thereby move just these needles away from the knitting cam system of the cam carriage.
German Democratic Republic patent 15 733 discloses a patterning arrangement of the type just referred to. Before the operating stroke of the cam carriage, pattern information is transmitted to the pattern-wheel jacks from a jacquard card laid onto the face of one facet of an indexible jacquard prism. After being thusly programmed, the pattern-wheel jacks are arrested in their programmed positions. The circumferential succession of pattern-wheel jacks are circumferentially spaced one per interneedle interval of the pattern-wheel circumference. During a cam-carriage stroke, the bolt-engaging portions of the selected pattern-wheel jacks act upon the pattern bolts of the selected needles, pushing the selected pattern bolts and thereby the selected needles out of the operative range of the knitting cam system of the cam carriage.
In the type of machine in question, the base pattern is limited in its breadth to a value corresponding to the circumference of the pattern wheel. If the width of the base pattern is to be increased, this requires the use of larger-circumference pattern wheels, such larger wheels, however, again having jacks which are circumferentially distributed one per interneedle interval. Because of space problems with this type of machine, the circumference of the pattern wheel cannot be readily increased, and certainly cannot be increased without limit. Thus, the largest base pattern to be horizontally repeated will have a width corresponding to the number of one-per-interneedle-interval jacks in the pattern wheel. The knitting of a base pattern whose width corresponds, for example, to twice the pattern-wheel circumference is not possible.
Additionally, with this type of machine, it is not possible for a pattern to be knit at just selected parts of the needle bed, e.g., plain knitting at the left and right thirds of the fabric and patterned knitting at the middle third of the fabric.
In view of these important patterning limitations, German Federal Republic published patent application DT-OS 2,424,836 discloses the provision of retracting devices on the needle bed, the retracting devices comprising elastic plates. These elastic plates are so arranged on the needle bed that they can move selected groups of successive needles from the operative vicinity of the knitting cam system of the cam carriage. Specifically, each such retracting device, when operative, removes a group of successive needles corresponding in number to the pattern-wheel circumference. The cam carriage is provided with selector means which when activated causes selected retracting devices to leave their respective groups of needles within the operative range of the knitting cam system on the carriage.
Thus, as the cam carriage performs a stroke, and the pattern wheel rotates repeatedly, the circumferential succession of jacks on the pattern wheel control needle groups during only preselected pattern-wheel rotations, whereas during the remaining pattern-wheel rotations the groups of needles passed by the pattern wheel are simply moved, in groups, away from the knitting cam system of the cam and therefore do not knit when the cam system passes them by. With this technique, it certainly is possible to knit in dependence upon the pattern information programmed into the pattern-wheel jacks, at only selected portions of the length of the needle bed. However, this expedient inherently decreases machine productivity, due to the many stretches of operation during which no knitting is occurring.